Clinical trials typically have something called a Data and Safety Monitoring Board, which periodically reviews safety (and, occasionally efficacy) data to decide if the trial should be halted prematurely. The DSMB is supposed to consider the potential benefits to the individual subjects and the population from which they're drawn, and weigh that against possible risks from the drug and the trial (e.g., complications from biopsies).
Since the subjects here are otherwise healthy men, who have other options for avoiding pregnancy, the DSMB should be fairly risk adverse and willing to kill the trial (as happened here). If, on the other hand, the trial were testing a new kind of anti-cancer therapy on patients with terminal cancer, the Board might be willing to tolerate a few more adverse events because the pay-off s are much higher.
The article seems to be saying, in a ham-fisted way, that the DSMB would have tolerated slightly more risk to women because pregnancy also carries its own risks.
